1. Field of the Invention
This invention relates to snowboards, and, more particularly, to improving the performance of a snowboard by designing it such that it will bow under a load into a curve of substantially constant radius.
2. Description of Related Art
When a snowboarder makes a turn, asymmetrical pressure is applied through the rider""s two feet to the snowboard. Ideally, the shifting of the rider""s weight should both rotate the board about its longitudinal axis, bringing the snowboard up onto one edge and balancing it there, and arch the snowboard longitudinally into a bow with the radius of curvature of the bow extending upwardly away from the snow""s surface. If this is achieved, the edge of the board will make a slender cut in the snow, the result of the back half of the board following in the track of the front half of the board, and the rider is said to xe2x80x9ccarvexe2x80x9d a turn. This is the ideal turn, for it cuts down on the friction or drag felt by the board as it travels through the snow. This is the easiest turn to control.
It is all too common, however, for the back half of the board to cut its own path through the snow. This is undesirable, for not only does it create control problems, it doubles the friction or drag experienced by the board. The main cause of dual tracking of a board on edge is that the longitudinal curvature of the board is not circular; inevitably it comprises a curve of varying radii, usually including an essentially flat portion in the middle of the board. If the edge of the board in contact with the snow were to form an arc with a single radius, i.e., the curvature of the cutting edge coincides with a segment of a circle, the back half of the board would have to follow in the same track as the front half. However, it is not easy for a snowboarder to control the forces applied by his/her two feet sufficiently finely to cause a board to have a constant radius of curvature; in fact, with existing boards, it is virtually impossible.
I have determined that the problem in carving perfect turns lies not so much in the skills of the rider as in the construction of the board itself, mainly in the resistance of current snowboards to being bent into a circular arc under the loads applied thereto.
Snowboards currently in the marketplace have bodies with vertical thicknesses which resist bending of the longitudinal dimension of the snowboard into a circular arc. Representative of the prior art are Remondet, U.S. Pat. No. 5,018,760, Carpenter et al., U.S. Pat. No. 5,261,689, and Nyman, U.S. Pat. No. 5,462,304.
Remondet shows (FIG. 4) a board having a single camber with the variation in thickness along its longitudinal centerline being a maximum in the center of the board and diminishing in both directions toward the tail and nose. Thus, not only does the center section have the least flexibility and thereby resists bending the most, but, because of the camber, the center section is convex, i.e., it is bowed with the radius of curvature pointing in the wrong direction, namely, downwardly toward the surface of the snow. A rider cannot apply any combination of pressures which will bend the central portion of the snowboard into a concave circular arc.
Carpenter et al. show (FIG. 1) a snowboard having thinner fore and aft sections separated by a thicker central platform having an essentially constant thickness. While being more flexible than Remondet""s board, the central platform is still the thickest part of the board, and consequently is resistant to bending.
Nyman shows (FIG. 2) a snowboard having a single camber and an essentially constant thickness from nose to tail (it is not clear whether the constant thickness is an intended characteristic of Nyman""s snowboard, or whether it is merely the draftsman""s contribution, for the thickness of the board is not mentioned in his specification). Nyman""s board acts more like a simple beam, and, if uniform in elasticity along its length, will bend essentially uniformly. The single camber, however, absorbs the bending effects, causing the board to straighten rather than to bow concavely.
Most prior art snowboards have a single camber, causing the usual prior art snowboard to contact the snow only with two widely separated segments of the snowboard near the nose and tail. The rider is supported between these segments, and although the distance between them is decreased as the camber is compressed slightly by the loading, the separation is still quite large. When turning, the snowboard will ride on the edges of these snow-contacting segments, which become in effect small arcs of an imaginary circle having a radius dependent on their separation. When the edge segments are widely separated, the radius of the circle is large, and the radius of the turn is large also. Smaller separations between edge segments produce sharper, tighter turns. Because of the inherent inability of prior art snowboards to bend in their central sections, they favor long, languid turns. Tight, abrupt turns are effected only by the rider imposing extremely complex combinations of weight shifts on the board. In effect, the rider has to fight the board in order to properly control it.
Most prior art snowboards include side cuts which narrow the central portion of the snowboard. Side cuts have two primary effects. One, they improve the board""s flexibility slightly, and although this contributes to its bowing, other design considerations (mainly their thicknesses and their single camber) tend to negate the effect. Two, the side cuts change the separation of the snow-contacting edge segments. Increasing (or decreasing) the amount of the compression of the camber decreases (or increases) the distance between them. These factors aid in the performance of the snowboard, but because prior art snowboards are inherently incapable of bowing, they are still very difficult to control.
The present invention overcomes the difficulties described above by providing a snowboard such that under normal loading, the snowboard will naturally bow into an arc having a radius which is substantially constant. Consequently, the edge segments of the snowboard coming in contact with the surface of the snow will substantially be portions of a circular arc, and the back half of the snowboard will substantially follow the track of the front half of the snowboard.
An explanation of the meaning of xe2x80x9cnormal loading,xe2x80x9d as used in the specification and claims, is appropriate here. When a rider is supported by a snowboard, the loading applied throughout the snowboard is defined by the length of the snowboard, the feet placement on the board, and the weight of the rider. The length of the snowboard and the weight of the rider is fixed for any given situation. Consequently, the loading depends on the placement of the feet on the board. The rider""s feet are secured to the snowboard by means of bindings fixed to the snowboard. The bindings are not usually limited to being attached to the snowboard in only one location, however. Provision is made for varying the location of the bindings both longitudinally and transversely of the snowboard, usually in the form of two arrays, one for each binding, of threaded inserts embeddded in the body of the snowboard. Each array, and its immediate surrounding area, defines a segment of the board which we are calling a xe2x80x9cmounting zonexe2x80x9d. Each snowboard has two mounting zones separated longitudinally along the length of the snowboard. When the bindings are secured within the mounting zones, the loading of the board by the rider is what is referred to herein as xe2x80x9cnormal loadingxe2x80x9d. It is the purpose of this invention, as will be brought out in more detail hereinafter, to provide a snowboard which, when subjected to loads within xe2x80x9cnormal loading,xe2x80x9d will bow into a reasonably close approximation of a constant radius arc.
It is therefore an object of the invention to provide a snowboard which is constructed to assist the rider in the carving of perfect turns.
It is a further object of the invention to provide a snowboard which, under normal loading, will flex such as to conform the body thereof to a reasonable approximation of a circular arc, thereby producing a turn which approximates the carving of a perfect turn.
It is a further object of the invention to provide a snowboard in which the flexures of the zones directly beneath the rider""s feet relative to flexure of the zone between the rider""s feet, in combination with the elastic properties of the materials from which the snowboard is constructed, permits the snowboard under normal loading to naturally bow into an arc having a substantially constant radius.
It is a further object of the invention to provide a snowboard in which the central section of the snowboard extending between the rider""s feet has a smaller Area Moment of Inertia than that under the mounting zones, thereby providing a flexure such that the board will respond naturally to the rider and assume the curvature of a segment of a circle.